JPH0328031B2 - - Google Patents

Abstract

A method for the manufacture of a radiant electrical heater, intended more particularly for heating glass ceramic hotplates, comprises so inserting or pressing helical heating resistors in helical slots in a support, such that the support or the heater coils themselves are deformed and consequently fixed to the support. The coils penetrate the wall or bottom areas of the slot or are otherwise secured by parts of the support by positive engagement. An apparatus for performing the method has a tool with ribs which deforms the support or heater coils for positive engagement. A radiant heater is obtained, whose support has partly overlapping deformations in the slot area of the heater coils.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electrically insulating plate, particularly suitable for glass-ceramic plates, comprising a carrier made of electrically and thermally insulating material, which has a groove in which a coiled heating resistor is fitted. This invention relates to a radiant heating element and a method of manufacturing the same.

With this type of radiant heating element it is always a problem to fix the heating coil in the groove so that it remains firmly attached during transport and use of the radiant heating element. What is important in this case is not only to prevent the coil from falling off, but also to prevent it from shifting (creep) in the longitudinal direction of the coil or groove. Thermal movements during heating and cooling promote a creep tendency that causes the individual sections of the coil to come together more tightly or to break apart. In the compressed area, strong heating phenomena occur that can prematurely damage the heating resistor.

Traditionally, heating coils of this type have been fixed in the grooves with heat resistant cement or putty. If the grooves are to be formed so that the protrusions or depressions are already formed at the stage of manufacturing the carrier, it will be very difficult to fit the heating coil into the grooves.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to propose a radiant heating element that can be securely fixed with little effort and without the use of auxiliary means such as putty or cement, and a method for producing the same.

This object is solved by the features of an electric radiation heating body according to the features of patent claim 1 and of the method for producing this heating body according to claim 2.

That is, the groove structure that characterizes the invention of the present application will be specifically explained using FIG. 1 and FIGS. 3 to 9 as follows.

The electric radiant heating body according to claim 1 comprises a carrier 16, 16b-1 made of an electrically insulating and thermally insulating material and having grooves 19, 19b-19e.
6e, with heating coils 20, 20c, 20 in the grooves.
In the electric radiation heating element in which e is partially buried, the carriers 16, 16b to 16e are made of a fibrous material or a ceramic material that can be hardened during the manufacturing process, and both side walls 21, 21b, 21d of the groove are
The heating coils 20, 20c, 20e have push-in portions 23, 23c, 23d which match the shape of the heating coils 20, 20c, 20e and in which the heating coils are tightly housed. 20
The largest part of the side area e in the groove width direction is inside the groove, and the side wall parts of the groove cover the side area of the heating coil in the groove opening direction, and there is a biting shape between the heating coils. It is related to.

Further, the method for manufacturing an electric radiant heating body according to item 2 also includes supporting members 16, 16 made of an electrically insulating and thermally insulating material having grooves 19, 19b to 19e.
b to 16e, with heating coils 20, 20 in the grooves.
In the method for manufacturing an electric radiation heating body, the heating coil 2 is partially buried.
0, 20c, and 20e, the largest part in the groove width direction is placed inside the groove, and at least the groove side wall portion 2
1, 21b, 21d and heating coils 20, 2
0c and 20e in a lateral direction relative to each other until the side wall portions of the groove overlap the side areas of the heating coil in the direction of the groove opening and are engaged between the heating coils in a biting manner. It moves and deforms the carrier.

With these arrangements, the heating coil is thus fixed within the groove by being pushed into the material of the carrier itself. The fixing itself is done directly when the heating coil is inserted or subsequently.
There is no essential time loss. Tools used for push-fitting or compression are incorporated into the coil-fitting process to enable this process. Fixing can be achieved by forcing the heating coil into a groove in the formation that is slightly shorter than the heating coil.
The heating coil is then easily pushed into the groove side wall (possibly with slight deformation of the heating coil cross section) and is very securely fixed. It is also possible to push it into the groove bottom, in particular into the ridge provided there. Furthermore, when fitting the heating coil into a matching groove, the heating coil may be tightened from above, for example, so that the cross section changes from a circular shape to an elliptical one, and the narrow side of the resulting elliptical shape is pushed into the groove side wall. Furthermore, after the heating coil has been fitted into the matching groove, the web provided between the grooves, i.e. in the region of the groove side walls slightly above the coil,
It is possible to caulk the heating coil so that it has a covering area. In this case as well, the heating coil can be pushed into the groove side wall.

In these embodiments, it is likewise possible to carry out the press fit even when the carrier made of insulating ceramic material or fibrous material is completely cured. However, it is also possible to carry out the press-fitting or crimping before the carrier is hardened, for example by baking or drying. In this case, a push-fit of the heating coil is possible with very small resistances, so that the method is also applicable to very thin heating coils. However, it is also possible to insert the heating coil into a corresponding groove in the still wet, uncured carrier and then carry out the curing or baking process. The shrinkage of the carrier material also reduces the size of the groove and forces the coil into the groove wall.

In principle in all embodiments it is possible to fix the heating coil by pushing it into the groove wall over its entire length. However, if the stability of the heating coil is sufficiently great that it is not necessary to fix it in the gap, for example due to the large thickness of the wire, then a certain spacing can be achieved by providing suitable projections and notches in the groove wall. It is also possible to only partially fix it.

Other advantages and features of the invention are apparent from the exemplary embodiment section and the description in conjunction with the drawings. The invention will be explained in detail below with reference to embodiments illustrated in the accompanying drawings.

FIG. 1 shows a radiant heating element 11 installed below a glass-ceramic plate 12 forming the cooking surface of the cooking utensil. The radiant heating element 11 is supported by a spring 14 on a carrier component 13, which is constructed, for example, from a sheet metal tank. The radiant heating element can partly pass through the glass-ceramic plate 12, and on the other hand serves to heat the cooking container placed on the glass-ceramic plate by means of the radiation that heats it. Radiant heating body 11
It consists of a normally circular, shallow carrier 15 made of a thin plate, in which a carrier 16 made of an electrically and thermally insulating material is housed. The carrier can be made of a ceramic insulating material or an insulating material consisting of inorganic fibers. The carrier 16 also has the shape of a shallow circular dish and, under the action of an essentially flat bottom 18 and a spring 14, holds the glass-ceramic plate 1.
It has an upright edge 17 which is pressed against the underside of 2. In this embodiment, the carrier 16 has a spiral groove 19 in which an electrical heating resistor in the form of a heating coil 20 is present. The arrangement and fixing of the heating coil in the groove will become clearer from the following figures. The heating resistor is connected to a household power source through a switch or a cooker.

FIG. 2 shows the arrangement of the heating coil 20 in the groove as a reference example. In this reference example, a heating coil with a circular coil cross section is received in a groove, the width of which corresponds to the outer diameter of the coil.
On the other hand, its depth is shallower than the coil diameter. Groove 19a
The groove bottom 22 is provided with a central protuberance 31 which can be constructed from a rib that goes around the groove longitudinally or from several protrusions on the groove bottom. thus,
The heating coil is pressed into the groove in such a way that it abuts the groove side walls and is thereby better guided laterally, but is also pressed into the bulge 31 .
As a result, the heating coil is firmly fixed in the lower region, especially in the longitudinal direction of the groove and the coil. That is, the ridge is deformed so that an engagement occurs between the ridge and the heating coil. In addition to the longitudinal fixation of the groove, the carrier 16a is deformed in the region of the protuberance so that it does not protrude upwards, but this arrangement, although advantageous, is not as important as the longitudinal fixation.

In the embodiment of the invention according to FIG. 3, a groove 19b is provided which is somewhat narrower than the outer diameter of the heating coil. The groove bottom 22 is flat. heating coil 2
0 when the heating coil is pressed into the groove side wall portion 21b.
Since it is laterally pressed into the groove, an indentation 23 is created there, which also serves for a particularly good fixing in the longitudinal direction of the groove. Furthermore, since the depth of the groove is shallower than the outer diameter of the coil, the upper part of the coil protrudes above the carrier 16b, improving the radiation relationship in this area. However, the groove is preferably deeper than the radius of the heating coil so that the widest point of the heating coil is still within the recess 23.

FIG. 4 shows the carrier 16c in another embodiment after the heating coil 20 has been inserted, but before it is finally fixed. Groove 19c
The width of the heating coil 20 corresponds to the outer diameter of the heating coil 20 having a circular cross section when fitted, the depth of the groove is between the coil radius and the coil diameter, and the heating coil is fitted into the groove 19c. Thereafter, a tool 24 in the form of a plate with downwardly projecting ribs 25, triangular in this example, extending longitudinally and concentrically above the groove 19c, acts on the heating coil. .

As can be seen from FIG. 5, the above heating coil has a horizontally rounded B-shape, and the outer side of the deformed heating coil 20c on the side where the groove is open. Coil portion 26 is recessed. This deformation widens the overall shape of the coil, so that it is embedded in the side wall 21 of the groove 19c, where the push-in part 23 serves to fix the heating coil as in the embodiment according to FIG.
form c. Instead of the rib 25 having a triangular cross-section, it is possible to use a rib having any basic shape, for example a flat ellipse, each of which produces the most advantageous coil shape in terms of fixation and radiation properties. Moreover, the curvature in section 26 has the advantage that a larger part of the heating coil is located directly above, on the side facing the glass-ceramic plate.

Similarly, FIG. 6 shows a carrier 16d in an uncompleted state.
It is shown. The grooves 19d correspond to those of FIG. 4, but the carrier 16d of FIG. 6 is formed from a ceramic or fibrous material but has not yet been dried or baked to obtain its final hardness. do not have. In FIG. 6, the heating coil 20 lies snugly in the groove 19d, but without any depressions.

FIG. 7 shows the same carrier 1 after drying or baking.
6d is shown. During baking, the material of the carrier contracts, ie the carrier shrinks. In this case, in particular, the size of the groove 19d according to FIG. 6 is also reduced to the size of the groove 19d' according to FIG. By firing, therefore, a volume-insensitive heating coil is forced into the side wall 21d of the groove, into which the depression 23 has the same effect as in FIGS. 3 and 5.
form d. As in FIG. 3, a slight deformation of the heating coil may also occur due to the lateral push-in, but this deformation can be avoided, particularly in FIG. 3, by appropriate support during the push-in.

FIG. 8 also shows the preparation of the carrier 16e in such a way that the groove 19e is essentially wider than it is deep, into which a heating coil 20e with a flat elliptical coil cross-section can be fitted with sufficient fit. It is shown. After fitting the heating coil, the web 29
This web 29 is cut by a tool 27 having a triangular projection 28 on the lower side, which is arranged concentrically above.
9, they press against each other in the shape of rivet heads, as shown as deformations 30 (FIG. 9), thereby fixing the heating coil 20e, which remains essentially unchanged in shape. In addition to the longitudinal fixation achieved by the inward entry of the side wall portion 21e, the rivet head-shaped deformed portion 30 reliably prevents the heating coil 20e from falling off. The deformation between FIGS. 8 and 9 can also be made in the already hardened state or in the wet state, but in the wet state shrinkage during fixing (method according to FIGS. 6 and 7) may be helpful. becomes.

Especially if the problem is to fix very thin wires, which are also particularly dangerous with respect to creep.
This fastening method in combination with several of the described embodiments is particularly advantageous. On the other hand, in the case of relatively thick wires, it is possible to perform the fixing with fewer safety devices, for example, the partition between the grooves can also be partially eliminated or only partially present. . This results in better heat transfer properties. Particularly in the embodiment according to FIGS. 8 and 9, it is possible to provide the deformation 30 only partially in the case of thick wires. The depth of penetration of the heating coil into the wall of the groove consisting of the side and bottom walls depends on the winding diameter of the wire load, the specific load on the heated surface and the wire. In these embodiments, the heating coil is also preserved against tipping.
This can occur if the wire forming the heating coil loses tension such that when hot, the individual turns of the coil overlap laterally and fall over, leaving the heating coil unsupported.

The type of shaped body must also be taken into account when selecting these embodiments for fixing.
Therefore, for example, a molded body made of a relatively soft fibrous material is selected for fixing by pressing, which is carried out in a completely hardened state, and in the embodiment according to FIGS. 6 and 7, first of all The hard ceramic material after firing is a problem. In this case, the heating coil can also be inserted into a carrier body that has been previously dried or previously hardened, but not yet fully hardened.

As described above, in the electric radiant heating element according to the present invention, the carrier is made of a fibrous material or a ceramic material that can be hardened during the manufacturing process, and the groove has both side walls that match the shape of the heating coil. It has a push-in part in which the heating coil is tightly housed, and the largest part in the groove width direction of the side area of the heating coil is inside the groove, and the side wall parts of the groove are It covers the side area of the heating coil in the direction of the groove opening and engages between the heating coils in a biting manner, so that the heating coil is not supported during transportation or when subjected to alternating thermal loads of heating and cooling. It can be securely and easily fixed in the groove so that it does not fall off from the body and does not cause a creep phenomenon in the longitudinal direction of the groove.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a part of a radiant heating element and a glass ceramic cooking area. FIG. 2 is a detailed sectional view of a reference example. FIG. 3 is a detailed sectional view of an embodiment of the invention. Figures 4 and 5 show the manufacturing steps for two pieces each.
FIGS. 6 and 7, 8 and 9 show other embodiments. Codes in the figure, 16, 16a to 16e... carrier,
20, 20b to 20e... Heating coil.

Claims (1)

[Claims] 1. Support 16, 16b-1 made of electrically and thermally insulating material with grooves 19, 19b-19e.
6e, with heating coils 20, 20c, 20 in the grooves.
In the electric radiation heating element in which e is partially buried, the carriers 16, 16b to 16e are made of a fibrous material or a ceramic material that can be hardened during the manufacturing process, and both side walls 21, 21b, 21d of the groove are
The heating coils 20, 20c, 20e have push-in portions 23, 23c, 23d which match the shape of the heating coils 20, 20c, 20e and in which the heating coils are tightly housed. 20
The largest part of the side surface area e in the groove width direction is located inside the groove, and the portions of both side walls of the groove cover the side surface area of the heating coil in the direction of the groove opening, and there is a biting shape between the heating coils. characterized by being engaged with
The above electric radiant heating element. 2. Support 16, 16b-1 made of electrically and thermally insulating material with grooves 19, 19b-19e
6e, with heating coils 20, 20c, 20 in the grooves.
In the method for manufacturing an electric radiant heating body, the heating coils 20, 20 are partially buried.
The largest part of the side surface area c, 20e in the groove width direction is placed inside the groove, and at least the groove side wall portions 21, 21
b, 21d parts and heating coils 20, 20c, 2
0e are moved in the lateral direction relative to each other until the side wall portions of the groove overlap the side areas of the heating coil in the direction of the groove opening and are engaged between the heating coils in a biting manner. . The method for manufacturing the electric radiant heating body described above, which comprises deforming the carrier. 3. The method according to claim 2, wherein the deformation of the carrier body 16d is carried out by press-fitting the heating coil 20. 4. According to claim 2 or 3, the heating coils 20, 20e are fitted in before the material of the carriers 16d-16e finally solidifies and the deformation is carried out by contraction of the carriers 16d-16e. the method of. 5. Deforming the heating coil 20c by changing the coil cross section after fitting into the groove 19c,
The method according to claim 2 or 3. 6. Fit the heating coil 20 into a circular cross section,
The method according to claim 5, wherein the groove is compressed and deformed from outside the groove. 7. The method according to any one of claims 2 to 6, wherein the heating coil 20 is pushed into the groove side wall portions 21, 21b. 8 Groove side wall portion 2 into which the heating coil 20 is pushed
8. The method according to claim 7, wherein the portions 1 and 21b are formed at intervals from each other in the longitudinal direction of the groove. 9. The method according to any one of claims 5 to 8, wherein the coil cross section is formed into an ellipse by at least deformation, and the shorter axis of the ellipse is located in the radial direction. 10. The method according to claim 2, wherein the deformation of the carrier 16e is carried out by compressing at least a part of the web 29 between two adjacent grooves 19e of the carrier 16e. Method.